Artificial sources of natural radionuclides in environment

Burning of fossil fuel may be one of the sources of radium-226 and lead-210 in the atmosphere. In coal the concentrations of radium-226 were reported as 0.001 to 1.3 pCi per gram. In Polish coal the mean concentration found is 0.3 pCi per gram. Assuming that this is the mean world concentration of radium-226 in coal the total of 2 x 1015 grams of coal burned per year in the whole world contains about 600 Curies of radium-226. The collecting efficiency of the dust collectors used in the power plants ranges from 75 to 99.8 percent. The mean fraction of the burned coal solids transferred to the atmosphere of the Earth is usually higher than might be inferred from the performance of high efficiency collectors, and is accepted as being 0.34 to 6.0 percent. With the maximum value of the fraction transferred to the atmosphere about 150 Curies of radium-226 will be dispersed each year. If dispersed uniformly over the Earth's surface this amount of radium-226 would correspond to a fallout rate of 0.3 pCi/m2 per year or 0.0004 pCi per liter of rainwater, assuming that 800 mm per year is the mean precipitation rate. As the emission of fly ash takes place near the ground, such uniform dispersion is improbable and much higher local deposition should be expected. (U.S.)